1. Field of the Invention
The present invention relates to a spider assembly for an expanding shoe drum brake and more particularly relates to a spider assembly for an expanding shoe drum brake of the type utilizing a cantilever mounted anchor pin or pins.
2. DESCRIPTION OF THE PRIOR ART
Expanding shoe drum brakes, especially air or hydraulically actuated drum brake systems wherein arcuate brake shoes are pivotably mounted to a support or spider member non-rotatably secured to a portion of a wheeled vehicle for pivotal rotation about an anchor member or members into frictional engagement with a rotating annular brake drum for the purpose of retarding the velocity of the wheeled vehicle by the use of a brake actuating member, such as a displacable cam element, are well known in the prior. The brake actuating member, usually a rotatable cam element or a linear wedge element, is located between the adjacent ends of the pivotal brake shoes and secured to a rotatable cam shaft or to a linear actuation shaft, respectively, for translating oscillitory, generally linear motion from a power source, such as an air motor or the like, to the brake shoes. Examples of such prior art cam actuated drum brakes may be seen by reference to U.S. Pat. Nos. 3,497,037 and 3,096,857, both of which are hereby incorporated by reference.
The prior art cam and/or wedge actuated drum brakes may be classified as straddle type drum brakes wherein the web members of the brake shoes straddle the spider member or cantilever type drum brakes wherein the anchor member is cantilever mounted to the spider member and the brake shoe web or webs are located on one side of the spider member only. The present invention relates primarily to drum brakes of the cantilever mounted anchor pin type.
Cantilever mounted anchor pin type drum brakes are known in the prior art and typically comprise a spider member for non-rotational mounting to a portion of a wheeled vehicle and an anchor pin or pins cantilever mounted to the spider member and extending from one side thereof for providing a pivotal mounting of the brake shoes. As the cantilever mounted anchor pin type drum brake requires that the brake shoes be axially restrained on the anchor pin, the anchor pins were typically provided with an enlarged headed portion spaced from the surface of the spider member from which the anchor pin extends by a distance generally equal to the width of the brake shoe web or webs. As such anchor pins were typically of a complicated and specialized structure, they were usually produced by machining of a bar of stock having a radius at least as great as the enlarged headed portion of the anchor pin. As the cost of materials and the cost of machining such anchor pins was significant, the prior art anchor pin structures for cantilever mounted type anchor pins was totally satisfactory.